Many electronic devices, such as computers, personal digital assistants (PDAs), mobile telephones, compact disc and cassette players, and the like, are intended to be powered from both alternating current (AC) and direct current (DC) power sources. AC power sources include wall outlets, while DC power sources may include both batteries and vehicle power supplies, such as automobile cigarette lighters and airplane seat power supplies (such as the EMPOWER system). In order to receive power from these various AC and DC power sources, electronic devices must generally be provided with a number of separate power-converting power supplies. Moreover, each electronic appliance may receive operational power at a different required current or voltage. These operational requirements may also change depending on the status of the electronic device (e.g., whether the electronic device's battery is being recharged).
To power electronic devices such as computers, the manufacturer typically provides an external power supply. The external power supply may be a switching power supply that may weigh close to a pound and may be about eight inches long, four inches wide and about four inches high. In addition, the power supply may include a fixed output cable and/or fixed input cables and plugs, making it more difficult to be compactly stored.
Such external power supplies therefore contribute substantial additional weight that the user of the computer must carry with him or her to permit battery charging and/or operation from an electrical socket or other power source. Further, the external power supply can be bulky and may not be readily carried in typical cases for portable electronic devices, such as notebook and sub-notebook computers. Also, a separate power supply may be required for each peripheral device, such as a printer, external memory (e.g., a disk drive) or the like. Therefore, users need multiple power supplies, which consumes space and increases unnecessary weight. Each of these power supplies may be specifically designed for use with either a particular type of AC or DC power source. Therefore, particularly for portable electronic devices for which it is desirable to be capable of receiving electrical power from any of a number of AC and DC power sources, the user may need to continually carry multiple power supplies adapted for the variety of power sources that may be available.
Some of these deficiencies are addressed in U.S. Pat. Nos. 6,266,261, 5,636,110, 5,838,554, 6,091,611, and 6,172,884 to Lanni, which describe programmable power supplies. The output may be programmed by coupling interchangeable tips to an output cable or terminal of the power supply. A dual-stage power supply for converting AC and DC power input signals into a DC power output signal is also described. These patents, however, do not describe how the interchangeable tips may be conveniently and compactly stored to prevent damage and/or loss, which may be particularly important where the tips are small in size.
Other references that discuss power supplies capable of receiving both AC and DC power input are similarly deficient. For example, U.S. Pat. No. 6,172,891 to O'Neal et al. describes a power supply that has fixed input cables and plugs for receiving AC and DC power input signals and a fixed output cable and connector for providing a DC output to an electronic device. Moreover, the O'Neal reference does not describe any mechanism for converting the AC or DC input power signals into DC power output signals of various characteristics to match the input power requirements of more than one electronic device.
The power supply disclosed in U.S. Pat. No. 6,057,610 to Nierescher includes a fixed AC input plug to which a DC plug attachment may be fitted such that the power supply can receive a DC power input power signal. As with the O'Neal et al. patent, the input cable to the AC input plug is fixed. While the DC plug attachment and the output cable are shown as being potentially removable, the Neirescher patent does not disclose how these attachments are to be conveniently stored with the power supply.
U.S. Pat. No. 5,940,282 to Oglesbee also describes a power supply that includes a fixed AC input plug to which a removable DC input plug attachment may be coupled. No output cable, whether fixed, removable or retractable is described. Furthermore, as with the Nierescher patent, the Oglesbee patent does not disclose any mechanism for compactly and conveniently storing the input plugs and cables or the output cables.
Current AC/DC and DC/DC combination systems are bulky. Even in the event that the user only needs to use the DC/DC adapter in such a system, the user must also carry the AC/DC adapter, resulting in inconvenience for the user. If the user already owns an AC/DC converter, the user's AC/DC converter cannot be utilized to form a combination AC/DC and DC/DC adapter system. Instead, the user must purchase a new AC/DC and DC/DC adapter system.
It would be desirable to provide a power supply with a thin package and designed to fit within a standard pocket on a shirt or a standard calculator pocket on a brief case. In addition, it is believed to be desirable that the power supply be capable of receiving input power from either AC or DC power sources and be capable of providing a programmable output power to meet the requirements of a host of electronic devices.